The Operative Significance of the Supposed

Rudimentary Coccygeal Process.

 

The spinal configuration of all chordates determine each ones posture and mobility. Because of this, some various organisms can be classified taxonomically based on the length of their spine, the spine’s flexibility, its curvature, and many others. This is evident when one looks at the different types of hominoids. There are leapers (long spined), suspensory (relatively short spined), quadrupeds (short and thick), bipeds (medium length and flexible), et cetera. Because of this, many assume that the relative length of the spine is evolutionarily developed and each adaptation is based on how far along the evolutionary ladder the organism is presently at. Sufficient to say, such a notion includes the human spine.

The human spine is made up of twenty-four vertebra and one hundred and ten joints (NASS, 1). It is further divided into five sections, namely: the cervical spine, which is composed of five vertebra (of which the atlas and the axis is the most popular), the thoracic spine, which is made up of twelve vertebra and is where the rib cage articulates, the lumbar spine (the five largest vertebra which absorbs most of the pressure and impact in the spine), the sacrum, which attaches the whole structure to the pelvis, and the coccyx.

This structure, which is also known as the vertebral column or backbone, is one of the primary support structures for the human skeletal system. Due to its immense articulation, the backbone allows for a wide degree of movement, flexibility, and increased locomotive capability. This is especially made possible by the presence of cartilage found in between each vertebra, which are appropriately named the inter-vertebral disks. These disks absorb most of the pressure the spine experiences as it performs an extensive range of movements (sometimes all at the same time).

The human spine is the most unusual of all vertebral configurations because of its curvature. The S-shaped curve of this structure is an intrinsic feature that can be found in humans alone. Because of such an arrangement, humans are enabled to stand in an upright position and walk in a bipedal manner. Some animals, such as most terrestrial apes, are also capable of walking bipedally but cannot sustain this manner of locomotion in any length of time. This is because their backbones are not configured for such behavior. Theirs is shaped in a much shorter and straighter spinal arrangement hence greatly suited for quadrupedal locomotion. Therefore, their ability to move using their hind legs is merely a food gathering (and/or protection) technique, much like the elastic tongue of most reptiles and amphibians.

Such differences in vertebral arrangements, however, do not deter people from assuming that some ancestral apes did walk on hindlegs without the benefit of an S-shape curved spinal column. These people, obviously not very bright, presume that the laws of physics and geometry do not apply to such ancient species and that their over-all bone structures do not at all have anything to do with their modes of locomotion. In addition, some even get ahead of themselves by allegedly determining behaviors of different species without the benefit of a complete skeletal structure, much less a spine. Because of such drastic misconceptions, the different sectional functions of the human spinal column may be grossly misinterpreted.

The coccygeal process (or the tailbone), which is located at the caudal end of the spine, is defined in a variety of ways. The Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health does it in this manner, “the small bone caudal to the sacrum in man, formed by the union of four (sometimes five or three) rudimentary vertebrae, and forming the caudal extremity of the vertebral column.”(Miller, 273). Such a definition is the most common of all designations regarding the tailbone. This is because they state that due to the vertebrae’s small size and its fusion with other vertebrae, it is therefore conclusive that these structures are rudimentary in nature. In addition to this, one of the more interesting definitions regarding the coccyx is one supplied by the National Ankylosing Spondylitis Society. They state that, “the coccyx, or tailbone, is composed of from three to five rudimentary vertebrae....The articulation between the coccygeal vertebrae and the sacrum allow some flexibility in the coccyx, which is particularly beneficial in taking the stresses of sitting and falling. The coccyx is extremely susceptible to shock fracture....Furthermore, since a number of nerve pathways pass near this area, damage to the coccyx threatens damage to the nerves of the lower body...” (NASS, 4). In addition, NASS includes that the coccyx “helps protect the lower alimentary tract” (NASS, 1).

One should notice immediately after reading the above statement that the NASS’s definition greatly contradicts itself. This is due to the fact that their sentence starts off claiming that the tail bone is made-up of vestigial (therefore useless) bones that are fused together, then the definition is terminated by enumerating a variety of functions that the coccygeal process performs and its importance to the nervous system (as can be seen if and when it is damaged). This is like saying that the cranium is a group of rudimentary plates fused together at the sutures and that although useless, it is “particularly beneficial” when you hit your head. Incidentally, it also houses the brain and therefore “a number of nerve pathways pass within this area” and because of this, it perhaps protects the brain.

How can anyone state that the coccyx is vestigial when all bones function the same way the tailbone does? According to the Encyclopedia and Dictionary of Medicine, Nursing and Allied Health, the skeletal system’s function is to: give support and structure to the body, protect delicate internal organs, make movement possible, attach with muscles, and many others (Miller, 1139). Correct me if I’m wrong, but isn’t this what the coccyx is exactly doing? If the categories that automatically exclude any bones from being designated as vestigial are similar to the ones stated above, the coccyx, therefore, should not be considered rudimentary.

The above notion can be readily observed in a variety of ways. First off, when a person sits down, pressure is exerted on the coccyx. As a response, the tailbone moves forward to absorb most of the shock that sitting down entails (no pun intended) (The Coccyx, 1). This can (and should) be observed as an active reaction to stress the body is experiencing and is therefore a protective response by the “vestigial” tailbone. Another way to determine the importance of the coccyx is by looking at the different structures that are connected to it (since one of the main functions of the skeletal system is its connection with muscles and other formations). The coccyx is cranially connected to the sacrum. According to NASS, the articulation between these two, help function as a “shock absorber” (NASS, 4). At its periphery, the coccyx holds (along with the pubis and ischial spine) a sheet of muscle called the pelvic diaphragm (Virtual Hospital, 1). The pelvic diaphragm includes, the levator ani, perineal body, perineal membrane, and other small muscles (Miller, 352). Hence, as can be observed, the coccyx holds in place a variety of structures that are important in locomotion and the protection of different internal organs.

In conclusion, many would like to think that the coccyx, or tailbone, is in fact the last vestige of our once long tails. Because of this, many dismissed the importance of this structure in the hopes that everyone would agree that there was a smooth progression from apes to man. However, in actuality, the coccyx is just like any other bone in the human anatomy. It functions similarly by giving protection, support, rigidity, a place to attach muscles, and many others. The only problem it had was that its location was where a tail would normally be present. That, however, does not qualify it as the rudiments of a tail. Furthermore, had the coccyx not been there, the sacrum would automatically be considered the vestiges of an ancestral tail regardless of what its other functions were. Hence, the alleged uselesness of the caudal end of the spine is more imagined that factual. This is because no matter how many times a person assumes that the tail bone is useless, the fact still remains that this structure functions just like any other bone in the human anatomy.

Internet, The Coccyx. www.ozemail.com.au/~sjdando/the2.htm

Philadelphia: W.B. Saunders and Co.

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